If you must have this, get them while you can. This is not set by the laptop maker but again, by manufacturing of the LCD panels. The machines that make them are many millions so I'd be repeating why things are the way they are.
If you find your 4x3, you need to pull the trigger.
The Surface Pro 3 and the Chromebook Pixel both have 3:2 screens. That works out to close to 16:11, almost exactly in the middle between 16:10 and 4:3. That's great for those of us who like taller screens on small laptops.
Are more laptops on the way with 3:2 screens?
16:9 is great for desktop, but not great for spreadsheets on small laptops at business meetings. I often meet clients at coffeehouses, and if I take anything bigger than 12", it's likely to have to stay on my lap rather than on the table. I much prefer having it on the table.
For meetings like that, the only laptop dimension that matters is width. Depth and thickness are all but irrelevant. If a person brings a 14" or bigger, they often have to keep it on their lap. Those who bring 12" laptops more often have space to have them on the little table.
But spreadsheets on a 16:9 screen on a 12" laptop are a form of torture. There just isn't enough vertical space. They remind me of my very first laptop, a 386SX in the mid 1990s that was about 3" thick at the rear, and had a small, short screen. I don't miss it.
I have a 12" Lenovo X201, with a 2.66GHz i7. As far as I know it's the fastest 16:10 12" laptop ever made. I had planned to used it as many years as I could hold out, not wanting to downgrade to a newer 16:9. But these two 3:2 models give me hope that I won't have to try to use this X201 for another decade.
So -- are more 3:2 laptops on the way, or are the Surface Pro 3 and Chromebook Pixel just anomalies?